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141 Posts
My 5m was running poorly as of the tail end of my last rip in my '85. I pulled the plugs and found that the gap on #4 had closed right down to just about nothing. This was the problem as she is running superbly again now. What might cause this? I currently have some cheap ass Delco plugs in it as my new NGK's are on the way.
While I had the plugs out I decided to do a compression test. I came up with:
1- 146
2- 150
3- 143
4- 134
5- 134
6- 142
I know this is low in all cylinders. I have a slightly shaved and ported head as well, so I expected the comp's to be higher. I had not checked the compression for about 18 months. I was in the 160's in some cylinders then (before I rebuilt the head). I do burn a good deal of oil so it would only stand to reason that I could use new rings (I did not drop some oil in the chamber and re-test compression, maybe I should have) I have been looking for a good reason to buy a 6m and rebuild it, but this 5M seems to run really strong especially after my recent acquisition of a DT header and Brullen exhaust system. Am I missing a lot of HP with these compression numbers? Sorry for the ridiculously long post.
While I had the plugs out I decided to do a compression test. I came up with:
1- 146
2- 150
3- 143
4- 134
5- 134
6- 142
I know this is low in all cylinders. I have a slightly shaved and ported head as well, so I expected the comp's to be higher. I had not checked the compression for about 18 months. I was in the 160's in some cylinders then (before I rebuilt the head). I do burn a good deal of oil so it would only stand to reason that I could use new rings (I did not drop some oil in the chamber and re-test compression, maybe I should have) I have been looking for a good reason to buy a 6m and rebuild it, but this 5M seems to run really strong especially after my recent acquisition of a DT header and Brullen exhaust system. Am I missing a lot of HP with these compression numbers? Sorry for the ridiculously long post.
